1. Field of the invention
This invention relates to a fuel injecting apparatus mainly used for an engine of a vehicle.
2. Description of the Related Art
A conventional fuel injecting apparatus is disclosed in the Japanese Patent Laid Open No. 3 (1991)-172574 (the corresponding U.S. Pat. No. 5,104,046). As shown in FIG. 5, the fuel injecting apparatus disclosed in the prior art comprises a housing 100 including an air inlet 101 for introducing air under high pressure. A case 102 is fixed to the right end of the housing 100 shown in the FIG. 5. The case 102 includes a fuel inlet 103 for introducing fuel.
A bobbin 105 around which a coil 104 is wound is disposed in the housing 100. The coil 104 is capable of flowing electric current. A core member 106 which is located at the left side in a center hole of the bobbin 105 is fixed to the housing 100. A nozzle 107 is fixed to the core member 106.
A first movable member 108 is formed of magnetic material. The first movable member 108, which is able to be slid in the right and left direction shown in FIG. 5, is disposed at the right side in the center hole of the bobbin 105. The first movable member 108 is opposite to the core member 106 with a gap and forced in the right direction by a spring member 109. The first movable member 108 includes a fuel chamber 115 which is always connected with the fuel inlet 103 therein. A second movable member 110 which is also formed of magnetic material is located in the core member 106. The second movable member 110 is opposite to the first movable member 108 with a gap and the second movable member 110 is able to be slid in the right and left directions shown in FIG. 5. The second movable member 110 is formed in the C-shaped configuration. A rod member 112 which is provided in the fuel chamber 115 is fitted in an opening portion of the second movable member 110. A ball 111 which is formed of non-magnetic material is fixed on the left side of the second movable member 110. Further, a third movable member 116 is disposed in the core member 106 so as to be able to be slid in the right and left directions shown in the FIG. 5. The third movable member 116 is opposite to the ball 111 and the third movable member 116 includes a valve seat 117 so as to be able to be contacted with and separated from the ball 111 selectively at the right side thereof.
A spring member 113 forces the ball 111 to be rested on the valve seat 117 through the rod member 112 and the second movable member 110. The spring force of the spring member 109 is provided to be larger than that of the spring member 113.
A fuel passage 123 is disposed in the third movable member 116, The fuel passage 123 is connected with a mixture chamber 120 which is disposed in the core member 106, The fuel passage 123 is connected with the fuel chamber 115 when the ball 111 comes apart from the valve seat 117, The mixture chamber 120 is always connected with the air inlet 101 and partitioned from the fuel chamber 115 by a diaphragm 121.
A rod 118 which is inserted into the third movable member 116 is fit in the nozzle 107. The nozzle 107 has a fuel outlet 128 at a tip thereof, The rod 118 includes an outward opening valve 119 at the left end thereof shown in the FIG, 5 to open and close the fuel outlet 128. A fuel injecting passage 124 which is always connected with the mixture chamber 120 is disposed between the rod 118 and the nozzle 107. The third movable member 116 is biassed so as to close the outward opening valve 119 by a spring member 125.
An operation of the conventional fuel injecting apparatus will be described with FIGS. 5 and 6 hereinafter. The mixture chamber 120 is always filled with the air under the high pressure introduced by an air pump (not shown in the FIGURES) through the air inlet 101. Further the fuel chamber 115 is always supplied with the fuel under the high pressure which is higher than that of the air in the mixture chamber 120 through the fuel inlet 103.
When a small amount of electric current is flowed in the coil 104 indicated at D in the FIG. 6, the electromagnetic force which is smaller than the spring force of the spring member 109 is applied to the first movable member 108 and the other electromagnetic force which is larger than the spring force of the spring member 113 is applied to the second movable member 110. Therefore the second movable member 110 is attracted to the first movable member 108 against the spring force of the spring member 113 without the movement of the first movable member 108. Therefore the ball 111 comes apart from the valve seat 117 of the third movable member 116. Consequently, the fuel introduced into the fuel chamber 115 is supplied into the mixture chamber 120 through the fuel passage 123 to be measured. Finally the fuel in the mixture chamber 120 is supplied to the fuel injecting passage 124.
When a large amount of electric current is flowed in the coil 104 indicated at E in the FIG. 6 in the next process, the electromagnetic force which is larger than the spring force of the spring member 109 is applied to each of the spaces between the core member 106 and the first movable member 108 and between the first movable member 108 and the second movable member 110. Therefore the first movable member 108 is attracted to the core member 106 against the spring force of the spring member 109. Therefore the second movable member 110 which is continued not to be contacted with the valve seat 117 is forced in the left direction shown in the FIG. 5. When the ball 111 rested on the valve seat 117, the fuel chamber 115 is closed to the fuel passage 123. Later on the third movable member 116 is moved in the left direction shown in the FIG. 5 by the first movable member 108 against the spring force of the spring member 125 through the second movable member 110 and the ball 111. Therefore, since the outward opening valve 119 is opened, the fuel in the mixture chamber 120 with the high pressure air is injected out from the fuel outlet 128 through the fuel injecting passage 124. As mentioned above, a cycle of the operation of the conventional fuel injecting apparatus is formed with the measuring process (indicated at D in the FIG. 6) and the injecting process (indicated at E in the FIG. 6) of the fuel.
Under the condition of the high rotational speed of the engine, since the fuel injecting apparatus needs to inject an amount of the fuel, it takes a lot of time to measure the quantity of the fuel. However in accordance with the conventional fuel injecting apparatus, the measuring process and the injecting process are independent each other, therefore a longer measuring time brings a shorter injecting time under the condition of the high rotational speed of the engine. On the contrary, a longer injecting time brings a shorter measuring time under the condition of the high rotational speed of the engine, therefore the conventional fuel injecting apparatus can not inject a sufficient amount of fuel.